Low pressure processes for producing butene-1 polymers in granular form are known in the art. These prior art processes, however, have a number of shortcomings in terms of either, or both, the process employed and the polymer product produced, when considered from the perspective of producing granular stereoregular butene-1 polymers on a commercial scale.
U.S. Pat. No. 3,678,023 discloses a low pressure process which is conducted in liquified gas and results in the production of atactic, rather than isotactic, polybutene-1. Such atactic polymers have decidedly different utilities than isotactic polymers. Further, because of the nature of the process employed, and the product produced, the product must be precipitated with an alcohol in order to obtain the desired granular form of the polymer, and the polymer then has to be extensively dried to rid it of alcohol and residual monomer.
U.S. Pat. No. Re 26,517 discloses the gas phase preparation of isotactic polybutene in an autoclave, in the substantial absence of solvents, with a stereospecific catalyst. However, this process is a batch type process which is not amenable to long term continuous operation. In addition, the butene-1 polymer produced by such process has a relatively high content of oily low molecular weight products and amorphous materials.
U.S. Pat. No. 3,168,484 discloses the preparation of solid particulate olefin polymers from monomers including ethylene, propylene and butylene, in a gas phase fluidized bed process, in the absence of solvents, by polymerizing the monomer charge with liquid catalyst components adsorbed on porous supports such as silica. Although the process is said to be continuous, wide ranges of pressure and temperature are given, and no conditions are given, specifically, for the continuous preparation of granular isotactic butene-1 polymers. Further, the process apparently requires the use, as illustrated in the Examples therein, of a heat-treated catalyst.
U.S. Pat. No. 3,580,898 discloses the vapor phase preparation of solid granular isotactic polybutene-1 with stereoregular catalysts. The process is conducted in a rotating reactor employing very specific reaction conditions, as well as a very specific catalyst system, in order to avoid agglomeration of the polymeric product in the reactor. Thus, this process requires the use of graduated, and relatively low, levels of both temperature and pressure, as well as the use of a single metal alkyl co-catalyst, diethyl aluminum chloride. The use of other commonly employed metal alkyl co-catalysts is apparently not suitable in the process. Said co-catalyst, as well as the other component of the catalyst system, is fed to the reactor in a small amount of solvent. Because of the need for the rotary reactor, and special reaction conditions, particularly the very specific temperature controls, the possibility of using this process commercially is severly curtailed, if not eliminated.
U.S. Pat. No. 3,922,322 discloses the preparation of solid particulate olefin polymers from C.sub.2 to C.sub.10 olefins in a gas phase fluidized bed process, in the absence of liquid catalyst diluents, by forming a catalyst prepolymer, storing this catalyst prepolymer under hydrogen, and then feeding the catalyst prepolymer and co-catalyst into the reactor with hydrogen gas. Although butene-1 is included within the scope of the olefins defined as useful in the process of this patent, no conditions are given, specifically, for the preparation of butene-1 polymers. Butene-1 polymers made by this process would be expected to undergo a postpolymerization treatment for the removal of atactic fractions.
Ethylene homo- and co-polymers have been made commercially in granular form in gas phase fluidized bed processes with various catalyst systems, as disclosed, for example, in U.S. Pat. Nos. 4,302,565 and 4,303,771. In order to operate these commercially useful processes successfully, it is necessary to properly combine both process conditions and catalyst compositions for the specific monomer charges employed.